Lubricating compound and process of making the same



Patented Sept. 18, 1934 PATENT;

LUBRICATING COMPOUND AND PROCES$ OF MAKING THE SAME Leonard R. Churchill, Bayonne, N. .Js assignor three-fourths to Tide Water :Oil Company, yonne, N. 3., a corporation of New Jersey He Drawin Application February 3, Serial No. 590,635

6 claims. (or 87-49) The invention relates to lubricants and to the Because of the increased power and increased All speed of the moving parts of recently designed automobiles, it has been found that formerly suitable lubricants are not capable of providing safe lubrication. Especially in cars having hypoid gears, ithas been found that a sudden seizure may take place between the teeth of the driving pinion and those of the ring gear. Under the impulse of the comparatively large amount of power transmitted from the engine to the driving wheels'this seizure results in a rapid disintegration of the surfaces of the teeth. Thus in a few minutes one of the vital parts of the automobile may be ruined, due to inadequate lubrication. It has been found that lubricants such as those containing lead soaps and sulfur are effective in preventing seizure. That sulfur is effective in certain types of lubrication problems, notably those involving the lubrication incidental to the operation of cutting tools, has long been known. Up to the present time, however, all lubricants, containing sulfur, so far as known to this applicant, have had the sulfur added insuch a manner that it is more or less corrosive, as evidenced by its effect on a polished copper plate. In fact the current theories of the '35 effectiveness of added sulfur (usually added as flowers of sulfur) in cooling a hearing or preventing seizure have been based on the use of active sulfur, that is to say, to be effective the sulfur has to be present in such a state that it so will form a sulfide film on the surface of the bearing metals. It is known that copper sulfide, for example, is of such a nature that it is self lubricating, no lubricant being required to prevent seizure when a bearing having a film of copper sulfide is properly supported. Under the same conditions of load and speed, seizure takes place when the journal does not have a sulfide film.

The use of a polished copper plate described herein, as a testfor the state of the added sulfur, is based on the known sensitiveness of this material to the chemical action of elementary sulfur and many of its compounds. Thus, up to the present invention, a test of various sulfurized 'oils has invariably shown that the sulfur contained in these products was present in such a state that it would darken a polished copper plate, when heated in contact with the sulfur bearing oil for a period ofthree hours, at a tern perature of 122 F. Such a procedure has been a more or less standard test used for detecting the presence of undesirable sulfur in gasoline or allied products.

An object of the invention is to develop a lubricant serviceable under extreme pressure.

More specifically, the object is to provide lubricants containing sulfur combined chemically in such a way as to be non-corrosive.

Further, the object is to provide a type of non-corrosive sulfur-containing lubricating oil base, with which desired lubricants can be made by admixture with suitable amounts of appropriate mineral lubricating oils.

' The further object is to provide a method of manufacturing such lubricants and lubricating bases.

In order to make the lubricating oil base I use a fatty oil and add to this an amount of sulfur not in excess of that which can be completely combined with the oil in a state in which it is not corrosive. The proportions may vary considerably. I have found that proportions of fatty oil to sulfur of about 8 to 1 are satisfactory, though considerably less sulfur may be used in the base if desired. At present prices of corn.

oil it is economical to use no more of it than is necessary. The upper limit of sulfur that can be successfully combined for the purpose of the invention appears to be in the neighborhood of the proportions given, but this may vary with different oils and under different conditions.

The fatty oil and the sulfur are heated with agitation to a comparatively high temperature, until an exothermic reaction is started, which is usually in the neighborhood of 320 F. However, this temperature will vary more or less, depending on the conditions of agitation, etc. It is important that this reaction be carried to completion, or until test with a copper strip shows no corrosion. When it is finished, the result is a stable lubricating base, which is strictly non-corrosive, and which is well adapted for blending with various mineral lubricating oils.

As an example, the invention may be carried out as follows:

To 88.5 parts by weight of corn oil is added 11.5 parts by weight of flowers of sulfur. The mixture is heated with constant agitation until the exothermic reaction takes place. As stated, this. will occur in general at a temperature of about 320 F. The source of heat may be removed at this juncture and the temperature will continue to rise until a temperature of from about 400 to 420 F. is attained. The exact nature of the reaction taking place at these temperatures is not known, but it is believed that addition products are formed. It has been found that at 320 F. traces of of hydrogen sulfide are given off and at 400 F. considerable amounts are given off. A small amount of water is also formed as a result of the reaction, and it, therefore, appears that some substitution of hydrogen in the molecule of the fatty oil has taken place. That a definite chemical reaction takes place is indicated (1) by the exothermic reaction, which does not appear to have been observed by others, and (2) by the fact that the starting point of the reaction appears at approximately the same temperature for several fatty oils tried, and that the subsequent course of the reaction is similar. In large batches no further heat is added but stirring is continued for a suitable interval of time, which may vary from one hour to six hours or more, until it is found that a sample of this base will not tarnish a strip of copper immersed in it for a period of one or two minutes. The heat treatment here described constitutes a novel process in the manufacture of sulfurized bases, for it may be shown by suitable tests of the product before heat treatment that the sulfur is all chemically combined, but it is in such a state that although it can not be physically separated it is corrosive to copper. The subsequent heat treatment gradually converts the product into one which is non-corrosive to copper. This process may readily be followed by testing at intervals with a polished copper strip. By careful manipulation, it is possible to obtain'a sulfurized base by this procedure which will not tarnish, discolor, or otherwise stain or corrode a polished copper plate when the latter is immersed in the base for three or more hours at a temperature a of 210 F.

It has been found that other oils, such as castor oil, cottonseed oil; menhaden oil, linseed oil, and other vegetable or fish oils may be treated in a similar manner. Animal fats and oils give higher pour points for the lubricating oil bases, but when such bases are compounded with mineral oil, the pour points of the resulting lubricants are not, or need not be, raised above those of the respective mineral oil stocks. Oleic acid gives a product under the procedure outlined, which does not tarnish a polished copper plate, but does etch or corrode the copper, without tarnishing. in a manner probably connected with its acidic nature and not becauseof the sulfur. Mixtures of fatty oils may be used.

It is also to be noted that in common with many chemical reactions, the results obtained by the method outlined, may also be secured by operating at a lower temperature for a longer period of time. It is observed that the sulfurized bases as made by this process are dark red products, more viscous than the original oils, and have little odor. Thus the product obtained from menhaden oil can scarcely be distinguished in odor from that obtained from corn oil or cottonseed oil.

To make a finished sulfurized lubricant, from 5 to 25% of the above base is dissolved in a suitable heavy lubricating stock. The solution may be effected by mixing and heating to 200 F. or thereabouts. In the course. of experimenting with this base for making sulfurized lubricants for certain modern types of free wheeling transmissions, it has been found desirable at times to add the base to light paraifin oils and to heat to 350 F. to 400 F. to obtain a clear solution of the base in the mineral oil. Light lubricating oils from other types of crude also give satisfactory lubricants for this purpose when blended with the base. In some cases clarity has been obtained at lower temperatures. These products, while intended primarily for free wheeling. lubrication, may be used as a cutting oil. The viscosity-coefficient of a lubricant made in this way is approximately equal to, or better than, that of a straight Pennsylvania lubricating oil of the same viscosity at 210 F.

Mineral oil suitable for combining with the base for the preparation of regular transmissions and rear axle lubricants are lubricating oil stocks from any type of crude base having a viscosity of about 70 seconds Saybolt or over at 210 F., and are preferably those having a viscosity in Saybolt seconds at 210 F. of 90 to and 150 to 160. The pourpoint of these oils should preferably be about 0 F. in the first case and from 15 to 30 F. in the second. It is an advantage that the addition of the base, at least in amounts up to 10 does not increase the pour points of the lubricants. A small amount of pine oil or similar substance may be added, this ingredient having the effect of preventing or reducing foaming of the lubricant when in service.

Two typical formulae for lubricants suitable for lubrication under conditions of extreme pressure, such as those encountered at the points of contact of the teeth on modern automobile transmissions and rear axles, will now be given. The first formula isfor a lubricant for summer use, and the second represents a winter lubricant.

A lubricant made according to the above formula has under test prevented seizure in a bearing under a pressure of 26,000 pounds per square inch at a low speed of twenty-five revolutions per minute. An ordinary transmission oil would seize under these conditions at a pressure of 4000 to 5000 pounds per square inch.

A sulfurized transmission lubricant made as above has shown no visible tarnish or corrosion on a polished copper plate when immersed for 16 hours at 210 F. An amount of 0.01% of free sulfur will cause a black coating on a copper strip under these conditons in less than one hour.

An example of the preparation of a free wheeling oil suitable for present requirements is as follows:

With these proportions and materials, the compounded lubricating oil will have a viscosity of. 250 sec. Saybolt at 100" F. and 50 sec. at 210 F.,

the base raising the viscosity to this amount.

The amount of sulfur in the finished, compounded lubricants may range from about 0.5% to 5%. A greater amount of sulfur would scarcely be economical on account of the cost of the fatty oil.

While the formulae and directions given result in highly satisfactory products, it is to be understood that variations are permissible, and that the invention, in its broader aspect, is not confined to the particular proportions or exact temperatures or to the particular fatty oil, though corn oil is preferred.

While the copper plate test has been described, and is the best mode of detecting active or corrosive sulfur or sulfur compounds, it will be understood that the invention is not restricted to this test, and that other tests may be used, or that fixed operating conditions may be relied upon. I

Naturally the invention is not limited to the use of mineral oils alone with which to blend the base, since the mineral oil itself may be blended with animal, fish or vegetable oil.

I claim:

1. A process for preparing a non-corrosive lubricant base, which comprises adding to a fatty oil sufficient sulphur to completely combine with said fatty oil, heating to a temperature of about 320 F. to initiate an exothermic reaction, allowing this exothermic reaction to proceed until the mixture reaches a temperature ofapproximately 400 F. and holding the mixture at such approximate temperature until said base tests non-corrosive to copper.

2. A process for preparing a non-corrosive lubricant base, which comprises adding about 1 part of sulphur to about 8 parts of fatty oil, heating to a temperature of about 320 F. to initiate an exothermic reaction, allowing this exothermic reaction to proceed until the mixture reaches a temperature of approximately 400 F. and hold-.- ing the mixture at such approximate temperature until said base tests non-corrosive to copper.

bricant, which comprises adding to a mineral oil about 23-25% of a base prepared by adding to a fatty oil suflicient sulphur to completely combine with said fatty oil, heating to a temperature of about 320 F. to initiate an exothermic reaction, allowing this reaction to proceed until the mixture reaches a temperature of approximately 400 F., holding the mixture at such approximate temperature until said base tests noncorrosive to copper, and then heating the mixture of mineral oil and base until a clear solution is obtained.

4. A process for preparing a non-corrosive lubricant, which comprises adding to a mineral oil about 5-25% of a base prepared by adding about 1 part of sulphur to about 8 parts of fatty oil, heating to a temperature of about 320 F. to initiate an exothermic reaction, allowing this reaction to proceed until the mixture reaches a temperature of approximately 400 F., holding the mixture at such approximate temperature until said base tests non-corrosive to copper, and then heating the mixture of mineral oil and base until a clear solution is obtained.

5. A lubricant comprising mineral oil and about 5-25% of a base prepared by heating a mixture of fatty oil and suflicient sulphur to completely combine with said fatty oil to about 320 F. to initiate an exothermic reaction, allowing this exothermic reaction to proceed until the mixture reaches a temperature of approximately 400 F. and holding the mixture at such approximate temperature until said base tests non-corrosive to copper.

6. A lubricant comprising mineral oil and about 5-25% of 'a base prepared by heating about 1 part of sulphur with about 8 parts of fatty oil to about 320 F. to initiate an exothermic reaction, allowing this reaction to proceed until the mixture reaches a temperature of approximately 400 F. and holding the mixture at such approximate temperature until said base tests noncorrosive to copper.

LEONARD R. CHURCHILL. 

